Liquid transport and mixing system for dust



1967 RA. DENBROEDER 3,357,160

LIQUID TRANSPORT AND MIXING SYSTEM FOR DUST Filed Dec. 28, 1965 R M E 00 W 0 KEN A! E 7 4 W R 1 I. l- I E F. B 0 M H P m B 4 H 4 I0 6 10 4 0 3United States Patent 3,357,160 LIQUID TRANSPORT AND MIXING SYSTEM FORDUST Russell A. Denbroeder, Bloomfield, Mich. (5420 Van Ness, BloomfieldHills, Mich. 48013) Filed Dec. 28, 1965, Ser. No. 516,894 1 Claim. (Cl.55-120) This invention relates to mechanism for separating andcollecting particles entrained in flowing gas streams. The mechanism isparticularly useful in the sulphate process of paper pulp production forcollecting sulphur-containing ash particles which are entrained in thegas stream issuing from the sulphur recovery furnace.

Generally the gas stream having the entrained ash particles is passedthrough an electrostatic precipitator positioned directly above a liquidsump which receives a weak sulphate solution recovered from the pulpdigestion process. As the gas stream passes through the electrostaticprecipitator the entrained particles precipitate onto the collectorelectrodes and drop directly into the sump where they are assimilatedinto the weak solution by a continuously rotating paddle type agitator.The enriched solution is later fed to the recovery furnace forextraction of the recovered sulphur compounds.

In the conventional arrangement the electrostatic precipitator and sumpare both rectangular in plan cross section, while the agitator bladeshave a circular orbit or coverage; the blades therefore cannot reach thecorners of the sump, and sludge builds up in these corner areas. US.Patent 3,109,630 suggests the use of liquid jets to overcome the sludgeproblem. The present invention seeks to overcome the problem by the useof a circular sump.

When the precipitate is allowed to fall directly into the sump theparticles near the center sump area receive little or no agitationbecause the agitator blade areas near the agitator axis have very smalllinear speeds. There is thus the possibility of sludge formation in thecentral areas of the sump. The present invention attempts to overcomethis problem by providing a sloped shed or roof over the central sumparea, said shed being effective to direct precipitate-d particles intothe outer perimeter of the sump where the linear blade velocity issufficient to assimilate the particles into the sump liquid.

A general object of the invention is to provide an arrangement ofelectrostatic precipitator and liquid sump wherein the precipitate isreadily assimilated into the sump liquid without formation ofappreciable quantities of sludge.

In the drawings the single figure is a sectional view taken through anelectrostatic precipitator and sump embodying the invention. As shown,the precipitator includes a conventional elongated upright casing havingfour upright flat sides, two of which are shown at 12 and 14. The casingthus has a rectangular plan cross section. Arranged within the casingare the conventional ionizer wire electrodes 16 and plate type collectorelectrodes 18. The wires may be suspended from a charging frame 20 whichis connected with the conventional insulated high voltage terminals 22.Weights 24 may be used to hold the wires in their desired spaced-apartpositions.

Collector electrodes 18 may be suspended in any convenient manner, as bytransverse bars 26. Rapping or vibrating mechanisms such as those shownin US. Patent 1,551,724 may be utilized to periodically dislodgeprecipitate from the collector electrodes. In service, particleladen gasenters the precipitator through inlet 28, whereupon the particles areionized by wires 16 and are precipitated onto collector plates 18.Periodically, the plates are rapped to dislodge the particles, andpermit them 3,357,160 Patented Dec. 12, 1967 to gravitate toward theliquid sump 30. The clean gas proceeds through gas outlet 32.

Sump 30 has a circular plan cross section. Therefore the transition duct34 between it and casing 10 is built to a semifunnel configuration withflat upper wall surfaces gradually merging into arcuate lower wallsurfaces. The duct thus guides some of the falling particles into thesump.

Overlying the central portion of the sump is a conical roof or shed 36suitably supported from the sump side wall by three or more plate-likebrackets 38. The shed intercepts a major portion of the fallingparticles and directs them into the outer perimetrical portion of thesump where they can be most effectively assimilated into the agitatedsump liquid.

Introduction of liquid, such as weak sulphate solution, may beaccomplished through inlet opening 40 located some distance above outletopening 42 to establish a liquid level approximately even with the upperedges of agitator blades 44. The drive for the agitator blades may beeffected from a powered shaft 46 disposed within a tubular support 48which projects upwardly from the sump bottom wall. Affixed to the upperend of shaft 46 is a sleeve 50 which carries agitator blades 44 andscraper blades 52. Suitable bearings (not shown) may be provided tosupport the end thrust of shaft 46 and the side thrust of sleeve 50. Inany event, the arrangement should preferably be designed to givecontinuous rotary movement of agitator blades 44 and scraper blades 52from a single powered shaft.

As blades 52 move along the surface of conical shed 36 their serratedlower edges dislodge any particles otherwise tending to cling to theshed upper surface. The particles are thus discharged into the outerperimeter of the sump without excessive particle buildup on the shedupper surface. The outer portions of agitator blades 44 can be made tohave fairly substantial linear velocities, even with small rotationalspeeds of shaft 46. Therefore the particles fed to the outer blade areastend to be quickly dissolved or assimilated in the sump liquid. Shed 36thus keeps the particles away from the central area of the sump withoutexcessive particle buildup on the prevent sludge formation. The circularplan cross section of the sump is also effective to prevent sludge sinceit eliminates the corner areas of rectangular sumps which cannot bereached with a circular motion agitator.

I claim:

In combination, an electrostatic precipitator comprising an uprightmulti-walled casing having a substantially square plan cross section; aninlet in one of the casing walls for admitting particle-laden gas intothe casing; an outlet in another casing wall for discharging clean gasout of the casing; vertically disposed ionizer electrodes and collectorelectrodes arranged in the casing to intercept gas flowing from theinlet to the outlet, whereby solid particles are caused to precipitateonto the collector electrodes; said electrodes being spaced from oneanother to define vertical passages for allowing precipitate to fallinto the lower portion of the casing; a sump having a circular plancross section disposed below the rectangular casing; a convergentparticleguiding duct connecting the lower portion of the casing with theupper portion of the sump; the diameter of the sump being only slightlyless than the side-to-side dimension of the precipitator whereby theconvergent duct is steeply sloped for easy guidance of particles intothe sump perimeter; flushing liquid supply means fluidly communicatingwith said sump for admitting liquid to the sump; means at the perimeterof the sump for discharging liquid from the outenperimeter of the sump;a conical particle-distributing shed overlying the central portion ofthe sump; said shed having a downwardly-outwar'clly sloping uppersurface whereby particles deposited on the shed upper surface aredirected toward the outer perimeter of the sump; the diameter of theshed being only slightly less than the diameter of the sump whereby allof the precipitate will 'enter the sump immediately adjacent its outerperimeter; the aforementioned liquid discharge means being located belowthe level of the shed, whereby the shed will be entirely above the sumpliquid level; rotary agitator means centrally arranged in the sump formixing precipitated particles with the sump liquid; said'agitator meanshaving a diameter approximately that of the sump whereby to effectivelyreach the sump perimeter where the particles are deposited; poweredscraper means arranged to rotate about the axis of the shed, saidscraper means being located to traverse the shed upper surface wherebyto push particles toward the shed surface perimeter a tubular supportprojecting upwardly withinthe sump beneath the central portion of theshed; a sleeve surrounding the tubular support; a drive shaft extendingupwardly within the tubular support to a driving connection with thesleeve; and said scraper means being connected with an upper portion ofthe sleeve, and said agitator means being connected with a lower portionof the sleeve.

References Cited UNITED STATES PATENTS 1,551,724 9/1925 Anderson -112 X1,573,376 2/1926 Dickerson et 211. 55-145 X 1,668,063 5/1928 Force210-528 X 1,736,842 11/1929 Wilcox 210-528 X 1,798,510 3/1931 Winslow eta1. 55-426 1,944,523 1/1934 Miller 55-118 X 2,336,017 12/1943 Jewell eta1 55-431 X 2,373,154 4/1945 Welp 210-528 X 2,603,307 7/1952 Richardson55-108 2,614,652 10/1952 Sultzer 55-120 2,682,314 6/1954 Davis 55-1202,689,019 9/1954 Roberts et al 55-120 X 2,749,212 6/1956 Crowder 55-112X 3,109,630 11/1963 Nichols 55-101 X FRANK W. LUTTER, Primary Examiner.

HARRY B. THORNTON, Examiner.

D. TALBERT, Assistant Examiner.

